#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define rep(i, a, b) for (int i = (a); i <= (b); i++)
#define per(i, a, b) for (int i = (a); i >= (b); i--)
#define endl '\n'
const int N = 2e5 + 5;

int n, m;
int a[N];

int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> n;
  rep(i, 1, n) {
    int x, y;
    cin >> x >> y;
    x -= y;
    a[i] = x;
    a[i + n] = y;
  }
  int mx = max(a[1], a[2]), mn = min(a[1], a[2]);
  rep(i, 3, n * 2) {
    if (a[i] > mn) swap(mn, a[i]);
    if (mn > mx) swap(mx, mn);
  }
  cout << mx + mn;
  return 0;
}